1. Field of the Invention
This invention relates to a blowout preventer stack landing assist tool for use with a telescoping joint having a riser string and blowout preventer stack secured to the lower end of said telescoping joint. Such assemblies commonly are used in offshore oil and gas drilling operations performed from a semisubmersible drilling rig or a drilling platform.
Offshore oil and gas drilling operations utilize a wellhead housing supported on the ocean floor with a blowout preventer stack secured at its upper end. A blowout preventer stack is an assemblage of blowout preventers and valves used to control well bore pressure within the wellhead housing. The upper end of the blowout preventer stack has an end connection or riser adapter that allows the blowout preventer stack to be connected to a series of pipes, known as riser or riser pipe, connected in end to end relationship to form a riser string. This riser string extends upwardly to the drilling rig or drilling platform positioned over the wellhead housing.
In order to prevent the riser string from collapsing under its own weight, it is necessary for the riser string to be supported at the ocean surface by the drilling rig. This support takes the form of a hydraulic tensioning system and telescoping joint that connect to the upper end of the riser string and maintains tension on the riser string so it will not collapse. The telescoping joint is composed of a pair of concentric pipes, known as an inner and outer barrel, that are axially telescoping within each other with the upper interior end of the outer barrel sealing against the exterior of the inner barrel. The lower end of the outer barrel connects to the upper end of the aforementioned riser string. The hydraulic tensioning system connects to a tension ring secured on the exterior of the outer barrel of the telescoping joint and thereby applies tension to the riser string. The upper end of the inner barrel of the telescoping joint is connected to the drilling platform. The axial telescoping of the inner barrel within the outer barrel of the telescoping joint compensates for relative elevation changes between the rig and wellhead housing as the rig moves up or down in response to the ocean waves.
Oil and gas drilling operations as described above occasionally are performed with multiple wellhead housings positioned in a grid pattern in a supporting structure known as a manifold placed on the ocean floor. In this type of operation it is necessary to lift the riser string and blowout preventer stack upwardly off one wellhead housing to allow the rig to be moved and the riser string and blowout preventer stack lowered onto the next wellhead housing. Current practice has required disconnection of the telescoping joint, tensioning lines and associated piping from the riser string in order to be able to lift the blowout preventer stack high enough to move to another wellhead housing. There is therefore a need for a tool that would allow lifting and moving of the riser string and blowout preventer stack without requiring disconnection of the tension joint, tensioning lines and associated piping from the riser string connection. The blowout preventer stack landing assist tool of the current invention offers such a tool that is easily useable without requiring any of the time consuming and costly disconnection and reconnecting procedures currently required.
2. Description of Related Art
No related art is known at this time.